Companies buying new PCs to avoid the end of support for Windows XP helped the computer industry dodge an even gloomier quarter, IDC said Thursday.

Although the research firm was unable to quantify the impact that migrations had on PC shipments in the quarter ending June 30, there's circumstantial evidence to support the idea that an "XP effect" was finally at work.

"There are things to look at," said Bob O'Donnell of IDC. "One is to look at the vendors who traditionally have more enterprise sales. There, Dell stands out. It gained about four points in share in the U.S. [last quarter] and about a point globally. Dell has been focused on commercial sales, so the implication is that [the increase in share] is due to Windows XP."

On Wednesday, both IDC and rival researcher Gartner released their PC shipment estimates for the second quarter; each detailed yet another contraction, with IDC saying shipments declined 11.4% while Gartner pegged the downturn at 10.9%.

Those numbers were slightly smaller than the declines in the first quarter, when IDC reported a year-over-year drop of 13.9%, a record, and Gartner said the business shrank by 11.2%.

Some of that small improvement between first and second quarters can be attributed to replacement PCs purchased by businesses trying to dump the 12-year-old Windows XP, which Microsoft will retire in April 2014.

"The U.S. market is beginning to reflect some of the Windows XP to Windows 7 transition we've been expecting in the commercial PC space, as evidenced by the strong growth in the enterprise-focused Dell PC business," O'Donnell said in a statement accompanying the second-quarter estimates.

Lenovo provided a similar clue, O'Donnell said in an interview Thursday. The Chinese PC maker's share of U.S. shipments rose about two percentage points and nearly that much worldwide. Like Dell, Lenovo does the majority of its PC sales with businesses.

"We have been saying, 'It's got to come,' " O'Donnell acknowledged. "Why hadn't it shown up earlier? I don't know. Maybe companies are really waiting until the last minute."

Microsoft's warnings to customers that they ditch Windows XP have been growing insistent as the April 2014 deadline looms larger. That's not surprising, as Microsoft makes money only if users upgrade to a newer OS.

But even Microsoft seems disinterested in discounting OS upgrades enough to tempt customers into giving up XP: An April promotion that cut the price by 15% of Windows 8 and Office 2013 lapsed June 30.

O'Donnell also speculated that the Windows XP effect hasn't been as large as expected -- and thus not noticeable in its regular shipment tracking -- because more users are upgrading in place, eschewing new PC purchases to instead replace XP with Windows 7 on their older hardware.

"We've been hearing that a fair number of people are upgrading in place, something that didn't really happen with previous cycles," said O'Donnell, adding that PCs bought in the last three to five years, the typical replacement cycle for corporate PCs, are able to run Windows 7. "That's different than in previous [OS] changes, when you really had to have new hardware to upgrade."

There is an enormous number of PCs running Windows XP around the world. According to Web analytics company Net Applications, 37% of all personal computers ran XP in June, representing an estimated 570 million machines. Microsoft recently put that number at a much smaller 160 million, but did not reveal how it arrived at its figure. Even Microsoft's smaller number is gigantic, equivalent to more than two quarters of global PC sales at the current rate.

In a talk at this week's Worldwide Partners Conference, a Microsoft executive said the company expected that 10% of all PCs would still be running XP come next April, a percentage much lower than outside analysts' estimates, which have been as high as 25%.

Net Applications' statistics, meanwhile, hint that XP's presence will be even stronger than analysts anticipate: If Windows XP's current rate of decline continues, the aged OS will still power nearly a third of all PCs in April 2014.